Method of making arthroscope having a shim for angularly orienting illumination fibers

ABSTRACT

A method for forming an arthroscope having an inclined angle of view includes providing an inner lens tube member, an outer tube member, and an annular shim member. The annular shim member is positioned about an outer peripheral portion of the inner lens tube member and includes an upper portion defining an outer positioning surface and side edges angularly offset relative to an optical axis. The inner lens tube member and annular shim member are positioned within the outer tube member while a plurality of optical fibers are positioned therebetween. The optical fibers are oriented about the outer positioning surface and side edges such that the optical fibers are angularly offset relative to the optical axis. Alternatively, a shim member may be provided that is arcuate and defines a cross-sectional dimension approximating a maximum inner dimension of the outer tube member, wherein the shim member engages the outer tube member to stabilize the inner lens tube member therein.

This is a U.S. application Ser. No. 08/217,502 filed Mar. 24, 1994, nowU.S. Pat. No. 5,554,100.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to endoscopic instrumentation,and, more particularly, to a disposable rigid arthroscope having adirection of view offset relative to the longitudinal axis of thearthroscope.

2. Description of the Prior Art

Endoscopes have long been used in surgery to view internal portions of apatient's body through a narrow incision in the body exterior or througha naturally occurring hollow viscus. Endoscopes are long, slenderinstruments having a shaft which is either rigid or flexible, dependingupon the procedure being performed. In general, endoscopes include anobjective lens positioned adjacent a distal end, and an imagetransmission system which may include a fiber optic bundle, relay rodsor lenses, or a solid state sensor to transmit the image to the viewer.Endoscopes also are usually equipped with an illumination system, suchas a fiber optic bundle, which illuminates the area being imaged.Generally, a camera adapter is provided at the proximal end of theendoscope to permit the image to be displayed on a monitor for viewingby the entire surgical team.

Most endoscopes used for medical procedures have a fixed forward viewingangle. Different areas of the body can be imaged by changing theposition of the endoscope or, in the case of flexible endoscopes, bybending the distal tip. In these endoscopes, the objective lens isdisposed perpendicular to the optical axis of the instrument such thatthe area directly in front of the instrument is viewed by the user.

Some endoscopes have a direction of view which is offset relative to theoptical axis. Examples of endoscopes of this type are disclosed in U.S.Pat. No. 4,576,147 to Hashiguchi, U.S. Pat. No. 4,615,333 to Taguchi,U.S. Pat. No. 4,850,342 to Hashiguchi et al. and U.S. Pat. No. 5,184,602to Anapliotis et al. Such endoscopes, sometimes referred to as inclinedangle of view endoscopes, side viewing endoscopes or oblique angle ofview endoscopes, make it possible to thoroughly examine interior bodyspaces, such as the lining of a body cavity, e.g., esophagus, intestinalwalls and articular joint spaces, by rotating the instrument. Typically,these side viewing endoscopes incorporate an angle directing prism aspart of its objective assembly to redirect the field of view relative tothe optical axis. In accordance with the side viewing endoscope, theilluminating fiber optic bundle is typically orientated or bent at anappropriate angle at its light emitting distal end to direct light ontothe field of view.

One type of endoscope which may incorporate inclined angle of viewcapability is an arthroscope. Arthroscopes are used to examine theinterior structure of a body joint, for example, a knee, in order todetermine the extent of damage to the joint. Arthroscopes are typicallysmaller in diameter than other types of endoscopes, such aslaparoscopes, to enable the scope to fit into the relatively smalljoints of the bone, particularly the wrist and foot. Examples ofarthroscopes are disclosed in U.S. Pat. No. 4,838,247 to Forkner, U.S.Pat. No. 5,188,093 to Lafferty et al. and U.S. Pat. No. 5,190,028 toLafferty et al.

Known endoscopes and arthroscopes having an inclined direction of viewsuch as the scopes disclosed in the aforementioned patents have theirown particular shortcomings. For example, the construction of suchendoscopes is typically costly, thereby precluding the economicfeasibility that such scopes may be disposed after a single use.Furthermore, properly positioning and retaining the illuminating opticalfibers in a manner such that the light emitting end portions of thefibers directly illuminate light in the perspective visual fielddirection often entails substantial modification to the endoscopic tubeand/or the incorporation of adapters and/or attachments within thedistal end of the scope.

U.S. Pat. No. 4,576,147 to Hashiguchi describes an endoscope with aninclined angle of view wherein a tip member, positioned within each of alens carrying inner tube and an outer tube, and a saddle shaped pressingmember, soldered to the tip member of the inner tube, cooperate toorientate the optical fiber end portions in the visual field direction.A disadvantage of the Hashiguchi '147 endoscope is that the additionalcomponents e.g., the tip members within each of the inner and outertubes and the pressing member, need to be precisely manufactured inorder to be incorporated within the endoscope, thus increasing the costof the endoscope. Furthermore, such components require additional stepsin the assembly of the Hashiguchi '747 endoscope, further increasing thecost of manufacture of the scope.

A further disadvantage with the construction of known endoscopes of thetype having inclined angles of view concerns mounting the distal opticalcomponents within the distal end of the endoscope. For example, theendoscope described in U.S. Pat. No. 4,850,342 to Hashiguchi et al.incorporates several frame members which are fitted within the lenscarrying inner tube to mount the objective prism and the objective lenscomponents within the tube. The distal most cover glass of theHashiguchi '342 endoscope is mounted via a housing member and a separatefastening ring which is fitted within an opening in the housing member.

Accordingly, it would be desirous to provide a disposable endoscope,particularly an arthroscope, having an inclined angle of view that canbe manufactured and assembled efficiently. It would be further desirousfor such arthroscope to direct illuminating light in the field of viewwithout requiring extensive modification to the endoscopic tube memberor the incorporation of high precision fitting members and adapters. Itwould also be advantageous for the arthroscope to incorporate featuresto positively mount the objective lens elements within the distal end ofthe scope without requiring additional lens mounting components.

SUMMARY OF THE INVENTION

Generally stated, the present invention is directed to a disposablerigid arthroscope having an inclined angle of view. The arthroscopecomprises a frame member, an outer tube member extending distally fromthe frame member, an inner lens tube member eccentrically disposedwithin the outer tube member, optical means disposed within the innerlens tube member and having means for altering the field of view withrespect to the optical axis and an illumination system including aplurality of optical fibers. The optical fibers of the illuminationsystem are assembled and oriented to emit light in the general directionof the inclined field of view so as to sufficiently illuminate thesurgical field. The materials of the arthroscope are advantageouslyselected to minimize the overall cost of the scope while providing forhigh level optical performance.

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described hereinbelow withreference to the drawings wherein:

FIG. 1 is perspective view of the disposable arthroscope constructedaccording to the principles of the present invention;

FIG. 2 is an enlarged cross-sectional view taken along the lines 2--2 ofFIG. 1 illustrating the inner lens tube of the arthroscope mountedwithin the outer tube;

FIG. 3A is a cross-sectional view of the distal end of the inner lenstube of the arthroscope;

FIG. 3B is a transverse cross-sectional view of the inner lens tube ofthe arthroscope;

FIG. 4A is a distal end view of the distal cover lens of thearthroscope;

FIG. 4B is a side plan view of the distal cover lens of the arthroscope;

FIG. 5A is a distal end view of the prism for altering the angle of viewof the arthroscope;

FIG. 5B is a side plan view of the prism;

FIG. 6A is a side plan view of the distal end of the inner lens tubewith an optical fiber orientating shim member positioned thereabout;

FIG. 6B is a distal end view of the inner lens tube and shim;

FIG. 7A is a side plan view of the distal end of the arthroscope withportions of the outer tube cut away illustrating the orientation of theilluminating optical fibers about the inner lens tube and the shim;

FIG. 7B is a distal end view of the arthroscope further depicting theorientation of the optical fibers;

FIG. 8A is a side plan view of an alternative optical fiber orientatingshim and the distal lens of the inner tube depicting the shim prior topositioning about the lens tube;

FIG. 8B is a side plan view of the alternative shim positioned about theentire periphery of the inner lens tube;

FIG. 8C is an distal end view of the inner lens tube and alternativeshim;

FIG. 9 is a side plan view in partial cross-section of the housingportion of the arthroscope illustrating the light guide connector withan illuminating coupler positioned therein;

FIG. 10 is a plan view with parts separated of the light guide connectorand illuminating coupler illustrating the support member and the lighttransmissive element of the illuminating coupler;

FIG. 11A is a side plan view in partial cross-section of the couplersupport member of the illuminating coupler of FIG. 10;

FIG. 11B is an axial view of the coupler support member of FIG. 11A;

FIG. 12 is a side plan view of the light transmissive element of theilluminating coupler of FIG. 10;

FIG. 13 is a cross sectional view of the illuminating coupler of FIG. 10illustrating the light transmissive element mounted within the supportmember;

FIG. 14 is an optical schematic view of the objective lens assembly ofthe arthroscope of FIG. 1 illustrating ray path and image orientation;

FIG. 15 is an optical schematic view of the relay lens assembly of thearthroscope of FIG. 1 illustrating ray path and image orientation; and

FIG. 16 is an optical schematic view of the eye lens assembly of thearthroscope of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, in which like reference numerals identifysimilar or identical elements throughout the several views, FIG. 1illustrates, in perspective view, an arthroscope 100 having an inclinedangle of view constructed according to the principles of the presentinvention. Arthroscope 100 includes housing portion 200 and endoscopicportion 300 extending distally from the housing portion 200. Housingportion 200 supports eye piece assembly 220 which contains the eye lensassembly for viewing the image of the object formed by the opticalsystem of the arthroscope, and light guide connector 240. Light guideconnector 240 connects a light guide (not shown) which providesilluminating light to the illumination system of arthroscope 100. Thecomponents and function of light guide connector 240 will be discussedin greater detail below.

Referring now to FIG. 2, in conjunction with FIG. 1, endoscopic portion300 of arthroscope 100 will be discussed in detail. Endoscopic portion300 includes outer tube 310 and inner lens tube 320 disposedeccentrically within the outer tube 310. Outer tube 310 is preferablyfabricated from a rigid material such as stainless steel or the like.Inner lens tube 320 is also preferably fabricated from stainless steeland houses the optical components of the objective and relay lenssystems of the optical system. Inner lens tube 320 extends along theentire length of outer tube 310 and terminates within housing portion200 at a position adjacent the eye lens assembly as shown in FIG. 9.

Referring again to FIGS. 1 and 2, distal end surface 312 of outer tube310 is oblique or inclined, i.e., angularly offset relative to a planeextending generally transversely to the axis of endoscopic portion 300.In the preferred 30° arthroscope, the distal end surface 312 defines anangle of about 30° relative to the transverse plane. Similarly, distalend surface 322 of inner lens tube 320 is inclined at an angle "θ" (FIG.3A) which measures about 30°. Although a 30° angle is preferred, thepresent invention is not so limited and could be within a range from0°<θ<135°.

Referring now to FIGS. 2 and 3A-3B, distal end surface 322 of inner lenstube 320 includes a curved lip portion 324 at an upper portion of thelens tube. Lip portion 324 functions in mounting the distal opticalcomponents within inner lens tube 320 and also in positioning theoptical fibers of the illumination system as will be discussed ingreater detail below.

Lip portion 324 is preferably formed by initially curling the distal endsurface of a cylindrical tube inwardly and thereafter cutting the distalend at the prescribed angle, i.e., 30°, to provide the oblique distalend surface 322 with the lip portion 324 on a portion of the extremedistal tip portion of the tube. Preferably, the outer surface 325 of lipportion 324 defines an angle "α" (FIG. 3A) of about 60° with respect tothe longitudinal axis of inner lens tube 320 to concentrate illuminatinglight within the offset field of view.

Referring now to FIGS. 2, 4A-4B and 5A-5B, the novel method forpositively mounting the distal lens components of the optical system 400within inner lens tube 320 will be discussed in detail. FIGS. 4A-4Billustrate the distal most cover lens element 402 of the optical system.Cover lens 402 encapsulates the optical components within lens tube 320as shown in FIG. 2 and has a distal face 404 which, when mounted withininner lens tube 320, is angled at 30° relative to optical axis 400a ofthe optical system 400. Cover lens 402 also has a lower edge 406 whichdefines a generally arcuate cross-section and conforms to the shape ofinner lens tube opposite lip portion 324 when the top of cover lens 402is disposed against lip portion 324. The proximal face 408 of cover lens402 includes two projecting portions 408a, 408b, which mate to prism410.

Prism 410 redirects the field of view relative to the optical axis"400a" (FIG. 2) of optical system 400. Prism 410 includes lower andupper arcuate surfaces 412, 414 (FIG. 5A) which generally conform to theshape of inner lens tube 320 and a recessed or notched portion 411 atits proximal end to accommodate glue or adhesives which are used inmounting the prism within lens tube 320 and to an adjacent opticalcomponent. The optical characteristics of prism 410 will be discussed ingreater detail below.

During assembly, projections 408a, 408b are positioned within recess 416of prism 410 in the manner depicted in FIG. 2. Thereafter, projections408a, 408b are adhered to prism 410 by adhesives, cements or the like toform a one-piece assembled unit. Cover lens 402 and adhered prism 410are then inserted into the proximal end of lens tube 320 and advancedinto the lens tube until distal face 404 of cover lens 402 contacts lipportion 324 of the lens tube 320. Distal cover lens 402 and prism 410are positively constrained within inner lens tube 320 due to theengagement of edge 406 of cover lens 402 with the lower surface of thelens tube 320 and the engagement of upper edge 409 of cover lens 402with curved lip portion 324 of the lens tube 320. Furthermore, coverlens 402 and prism 410 are prevented from tipping proximally and/ordistally due to the engagement of lower and upper surfaces 412, 414(FIG. 5A) of prism 410 with the interior of inner lens tube 320.Similarly, cover lens 402 and prism 410 are prevented from rotating dueto the constraining action of curved lip portion 324. The remainingoptical components of the optical system, including the objective andrelay lens assemblies, are mounted within inner tube 320 by insertion ofeach component in the proximal end of the inner tube and mounting thesecomponents in a conventional manner.

Referring now to FIGS. 6A-6B and 7A-7B, the novel mechanism fororientating the optical fibers of the illumination system 500 to directilluminating light in the perspective visual field as provided by prism410 will be discussed in detail. An optical fiber orientating shim 330is positioned about the lower peripheral surface of inner lens tube 320.Shim 330 serves as a guide to position the end portions of eachillumination fiber 510 at a desired orientation so as to direct lightemitted by the optical fibers into the field of view of the arthroscope.Shim 330 includes two side portions 332 which are sloped downwardlytowards the lower portion of inner lens tube 320. In the preferred 30°arthroscope, each side portion 332 defines an angle "β" (FIG. 6A) ofabout 30° relative to the optical axis such that the illumination fiberend portions 510, disposed on either side of lens tube 320, are orientedat a 30° angle relative to optical axis 400a (FIG. 2), and perpendicularto distal end surface 322 of the inner lens tube 320. The remainingillumination fiber end portions 510 disposed adjacent the top of theinner lens tube 320 are oriented to direct light in the field of view bythe angled peripheral surface 325 of curved lip portion 324 at distalend face 322. Thus, sloped side portions 332 of shim 330 in combinationwith the peripheral surface 325 of curved lip portion 324 effectivelyposition and retain the end portions of illumination fibers 510 at thedesired 30° orientation in the assembled condition of arthroscope 100.As best shown in FIG. 7B, illumination fibers 510 are disposed in acrescent-shaped array about inner lens tube 320 within the space definedby outer lens tube 310, inner lens tube 320 and shim 330 when assembledwithin arthroscope 100. Preferably, the fibers 510 are placed onto theinner lens tube 320 about shim 330 and within the outer tube 310 priorto assembly of the optical assembly within the inner tube.

Shim 330 is preferably formed by replica molding techniques. In thepreferred method, a Teflon mold (not shown) made in the shape of theshim 330 is provided. The mold has sides angled at the desired curvatureof side portions 332 of shim 330. To form shim 330 directly onto innerlens tube 320, a drop of ultraviolet (UV) curing cement is placed at thebottom of the mold. Inner lens tube 320 is then oriented in the mold(related positioning fixtures may be used), causing the uncured cementto surround inner lens tube 320 in the shape of the mold. A UV light isthen activated to cure the cement. Inner lens tube 320 can then beremoved from the mold with shim 330 formed thereon. Replica moldingtechniques are desirable for forming shim 330 on inner lens tube 320 inthat such techniques are capable of forming precision shim componentsrelatively inexpensively and in large quantities. Further, such moldingtechnique positively fixes shim 330 to inner lens tube 320, thus,eliminating an assembly step which would otherwise be necessary duringmanufacture of arthroscope 100.

Shim 330 also assists in positively positioning inner lens tube 320within outer tube 310. As shown in FIGS. 2 and 7A-7B, the proximal endportion 331 of shim 330 preferably extends to the maximum inner diameterof outer tube 310 and fills the space surrounding the lower portion ofinner lens tube 320. Thus, inner lens tube 320 is prevented from side toside movement within outer tube 310 and up and down movement within theouter tube by the engagement of shim 330 with the inner walls of theouter tube.

In the preferred method for positioning illumination fibers 510 ofillumination system 500 about shim and within arthroscope 100, theillumination fibers 510 are placed into outer tube 310. Inner lens tube320, already cut at an angle and having curved lip portion 324 formedthereon, is inserted into outer tube 310 with the fibers 510 disposedwithin the space defined between the two tubes. At this point in theprocedure, the fibers extend out of both ends of outer tube 310. Acollar may be placed around illumination fibers 510 at the proximal endof outer tube 310 and the collar positioned within a jig. The jigpositions the collar, fibers 510 and tube 310 in the orientation theywill assume in the final assembled condition of arthroscope 100. A heatcuring cement is placed around the fibers at the collar and the entiredevice is heated to bond the fibers within and to the collar. A heatcuring cement is acceptable where glass fibers are used. If desired,particularly if plastic fibers are used, a UV curing cement may beutilized.

At the distal end of outer tube 310, illumination fibers 510 are dividedinto a middle (top) group and two side groups. Each group is bentdownwardly. The top group of fibers 510 is guided at the appropriateangle by curved lip portion 324 of inner lens tube 320. The side groupsof fibers are guided by shim 330. All groups are restrained in theirrespective positions by a fixture. Cement (which may again be heatcured) is applied to the three groups of fibers 510 and cured.

In the preferred method, cementing of the fibers at the distal end is atwo-step process. A low viscosity cement is first applied and is wickedalong fibers 510 inside inner tube 320. Suitable cements for thispurpose are manufactured by Epoxy Technology of Watertown, Mass., underthe tradenames EPO TEK 350ND and EPO TEK 350ND-T. The first cement isbaked to cure and a second, high viscosity cement is applied to fill anyvoids around fibers 510 at the distal end surface 322 and to act as asealant to prevent moisture and/or bodily fluids from contacting thelenses of the optical system. A suitable high viscosity cement isVitralit 1710 manufactured by Elosol Ltd. of Zurich, Switzerland. Thesecond cement is baked to cure. The excess ends of fibers 510 are cut,and the fiber surfaces at the proximal and distal ends are ground andpolished. If necessary, it is contemplated a sealant could be applied tothe distal end of the scope. The aforementioned Vitralit 1710 isappropriate for use as a sealant for this purpose. Once inner tube 320is fully assembled within outer tube 310, fibers 310 are compressed andretained at their appropriate angular orientation by side edges 332 ofshim 330 and surface 325 of inner lens tube 320.

Referring now to FIGS. 8A-8C, an alternative embodiment of the fiberorienting shim is illustrated. In this embodiment, shim 340 extendsabout the entire periphery of the distal end of inner lens tube 320.Shim 340 includes side portions 342 which are sloped downwardly at anangle relative to the axis of inner lens tube 320 in a similar manner tothat described in connection with the previous shim. Upper distalsurface 344 of shim 340 is also sloped downwardly. Side portions 342 andsloped upper surface 344 position optical fibers 510 in a mannersubstantially similar to that described in connection with the shim ofFIGS. 6A and 6B. In particular, the top group of fibers 510 adjacent theupper portion of outer tube 310 are guided by the angled surface ofdistal surface 344 of shim 340 and the side groups of fibers arepositioned by side portions 342. Thus, in accordance with thisembodiment of shim 340, it is not necessary to form the curved lipportion 324 of inner lens tube 320 to guide the top group of fibers.Shim 340 may be formed by conventional molding techniques or, in thealternative, by a replica molding technique. Optical fibers 510 aredisposed in a similar crescent shaped array as the embodimentillustrated in FIG. 7B.

Optical fibers 510 of illumination system 500 are each preferably glassfibers having a diameter which enables the fibers to be bent andoriented about shim 330, 340. In the preferred embodiment, fibers 510may have a diameter ranging from about 50 microns to about 90 microns.

Referring now to FIG. 9, in conjunction with FIG. 1, housing portion 200of arthroscope 100 includes two housing half sections 210. Half sections210 are preferably formed of a suitable plastic material such as ABS(acrylonitrile butadiene styrene), polycarbonate, polypropylene,polyethylene or the like, or, in the alternative, of a metal such asstainless steel, and are attached along a seam by suitable attachmenttechniques, including adhesives and/or ultrasonic welding. Eye pieceassembly 220 is secured within the proximal end of housing 200 byconventional means.

Referring now to FIGS. 1, 9, and 10, the novel mechanism for couplinglight into the illumination system of arthroscope 100 will be discussedin detail. By way of background, conventional light guides connected toa light source typically have a working diameter or illuminatingaperture of about 5 mm to correspond to conventional endoscopes whichalso typically have a 5 mm diameter entrance or illuminating aperture asdefined by the entrance end of the fiber optic bundle of theillumination system. However, since arthroscopes, including arthroscope100 of the present invention, are typically smaller in diameter thanconventional endoscopes, the entrance illuminating apertures of sucharthroscopes are also smaller. In particular, the entrance illuminatingaperture of arthroscope 100 of the present invention, as defined by theproximal entrance end 515 of fiber optic bundle 500 (See FIG. 9) rangesfrom about 2-2.5 mm. In order to minimize loss of light from a 5 mmlight guide, an illuminating coupler 242 is provided.

Referring now to FIGS. 9-13, illuminating coupler 242 is disposed withinlight guide connector 240 and includes support member 244 and a lighttransmissive optical element 246 disposed within the support member.Support member 244 is generally cylindrically shaped and includes agenerally frustoconical inner chamber 248 as defined by the taperinginner walls 250 of the support member 244. The lower portion of supportmember 244 includes three projections 252 which extend into chamber 248.Light transmissive element 246 is generally frustoconically shaped andincludes a circumferential ledge 254 at its larger diameter portion anda peripheral recessed portion or well 247 at its lower end portion. Inthe assembled condition of frustoconical optical element 246 withinsupport member 244 as shown in FIGS. 9 and 13, the frustoconical element246 is spaced from the support member 244 by an air gap. Such spacing isprovided by the engagement of projections 252 with the lower end portionof frustoconical element 246. Also, in the assembled condition,circumferential ledge 254 of frustoconical element 246 rests on theupper surface 256 of support 244 to assist in mounting the frustoconicalelement 246 within the support 244. The lower surface 245 offrustoconical element 246 and optical fibers 510 at proximal entranceend 515 are disposed in face-to-face relation as best shown in FIG. 9.Preferably, an epoxy glue is applied between lower surface 245 and theproximal entrance end 515 to maximize coupling efficiency between thefibers 510 and the lower surface 245. Recessed portion 247 offrustoconical element 246 accommodates any excess epoxy glue which mayoverflow into this area so as to ensure that a bead does not form at thelower end portion of the frustoconical element 246. The formation of anepoxy bead would degrade the light transmissive characteristics offrustoconical element 246.

Illuminating coupler 242 minimizes the loss of light when a light guidehaving a relatively large working diameter, typically 5 mm, is coupledto light guide connector 240 of arthroscope 100 which possesses anillumination aperture of about 2.5 mm. In particular, light entry side258 of frustoconical element 246 has a working diameter "a" (FIG. 12) ofabout 5 mm. The smaller diameter exit side 260 of element 246 which isadjacent the proximal end 515 of the illumination system has a diameter"b" of about 2.5 mm. Accordingly, light expelled from a 5 mm light guideonto entry side 258 of light transmissive element 246 is directedthrough the frustoconical element 246 and released from the 2.5 mmdiameter exit side 260 of the element onto the proximal end of theoptical bundle. Due to the differences in the indices of refraction offrustoconical element 246 (nd of about 1.5) and air (nd=1.0), the airgap defined between frustoconical element 246 and support 244 minimizesleakage of light from element 246 thereby ensuring maximum transfer ofilluminating light through element 246 and into illumination system 500.

Light transmissive element 246 is preferably molded of acrylic orpolycarbonate. The inner walls 250 of support member 244 may be groundfrom a 0.25 microfinish to about a 0.45 microfinish, which produces ahighly reflective surface to direct any stray light back into lighttransmissive element 246. The walls of light transmissive element 246may also be cladded with a reflective aluminum coating, which wouldobviate the need to suspend the cone in air.

Referring now to FIGS. 14-16, the optical system of the presentinvention is illustrated in detail. The optical system includes anobjective lens assembly (FIG. 14) for forming an image of an object, arelay lens assembly 440 (FIG. 15) for transferring the image throughendoscopic portion 300 and eye lens assembly 460 (FIG. 16) for viewingthe transferred image.

As shown in FIG. 14, objective lens assembly includes distal cover lens402, prism 410, first or distal doublet 420, triplet 422 and second orproximal doublet 424. An aperture stop may be provided between prism 410and first doublet 420 to limit the diameter of the light raystransferred through the system. Cover lens 402 is a plano concave lens.Prism 410 is preferably molded of a suitable polymeric materialincluding styrene, polycarbonate and acrylic or, in the alternative, maybe formed from an optical glass. The prism may also be formed of moldedglass.

Referring to FIGS. 5A-5B and 14, prism 410 is a 30° deflection prismwhich changes the direction of view of arthroscope 100 from forwardviewing to viewing at an oblique angle, i.e., at a 30° angle relative tothe optical axis of the optical assembly. In a preferred embodiment,prism 410 is a hybrid prism, i.e., one which principally reflects light,but, also refracts the light so as to change the angle of view. In thealternative and depending on the particular applications, prism 410 maybe a full reflection prism or a full refraction prism. A full refractionprism is preferably used when it is desirable to change the angle ofview less than 30° relative to the optical axis. Other suitable methodsfor altering the angle of view, such as mirrors and fiber optics, mayalso be utilized.

FIG. 14 illustrates ray path and image orientation through the objectivelens assembly. The geometrical characteristics of the objective assemblyare defined by an object plane 425a, surfaces 425b-c of cover lens 402,surfaces 425d-g of prism 410, surfaces 425h-425j of first doublet 420,surfaces 425k-425n of triplet 422, surfaces 425o-425q of doublet 424 andexit image plane 425r, respectively. The geometrical and opticalparameters of the objective assembly are recorded in Table 1 below. Inthe Table, surfaces A, B-C, D-G, H-J, K-N, 0-Q and R correspond toobject plane 425a, surfaces 425b-c of cover lens 402, surfaces 425d-g ofprism 410, surfaces 425h-425j of first doublet 420, surfaces 425k-425nof triplet 422, surfaces 425o-425q of second doublet 424 and exit imageplane 425r, respectively.

                  TABLE 1    ______________________________________                      THICK-                 ABBE    SURFACE RADIUS    NESS      MEDIUM INDEX NO.    ______________________________________    A       Object    (Object   AIR    1.000            Plane     Distance)    B       Plano     0.7       Styrene                                       1.590 30.9    C       0.800     0.7       AIR    1.000    D       -1.100    1.0       Styrene                                       1.590 30.9    E       Plano     1.4       Styrene                                       1.590 30.9    F       Plano     1.4       Styrene                                       1.590 30.9    G       Plano     0.2       AIR    1.000    H       19.763    1.0       Styrene                                       1.590 30.9    I       1.500     1.9       Acrylic                                       1.492 57.4    J       -2.062    0.3       Air    1.000    K       4.132     2.5       Acrylic                                       1.492 57.4    L       -1.500    1.0       Styrene                                       1.590 30.9    M       4.000     1.4       Acrylic                                       1.492 57.4    N       2.304     0.6       AIR    1.000    O       2.391     2.0       Acrylic                                       1.492 57.4    P       -4.300    1.5       Styrene                                       1.590 30.9    Q       -11.500   4.8       AIR    1.000    R       Exit Image            Plane    ______________________________________     *dimensions are in millimeters

Surfaces 425e, 425f of prism 410 are reflecting surfaces. Surface 425edefines an angle ranging from about 18° to about 26°, preferably about22.5°, relative to the optical axis while surface 425f defines an anglewhich ranges from about 4.5° to about 10.5°, preferably about 7.5°,relative to the optical axis.

The objective lens arrangement produces an inverted image of the objectat exit image plane 425r. As indicated in Table 1, the distance from theproximal lens surface 425q of second doublet 424 to exit image plane425r is about 4.8 mm. The inverted image formed by the objective lensarrangement is subsequently transmitted by relay lens assembly 440.

Referring to FIG. 15, a relay lens module 442 of relay lens assembly 440is illustrated in detail. Relay lens assembly 440 may include aplurality of relay lens modules, arranged in end to end fashion alongthe optical axis. Each module 442 is identical with regard to theoptical components contained therein, and is capable of transferring animage from an image plane at the entrance side of the module to asuccessive image plane formed on the exit side. Lens module 442 includestwo identical optical assemblies 444 arranged in symmetrical end to endrelationship relative to a median plane disposed between the twoassemblies. Assemblies 444 are separated by an air gap. Each assembly444 includes a glass plano cylinder 446 having an adjacent end face andan outer end face relative to the other component in the module. Glassplano cylinder 446 ensures the transfer of a bright image between themodules. Each assembly further includes a single lens 448 bonded to theouter end face of plano cylinder 446 and a single lens 450 bonded to theadjacent end face of the cylinder. Single lens 448, 450 are eachpreferably a plano-convex lens. The convex surface of lens 448, 450 maybe coated with a broad band anti-reflection coating to reduce reflectionlosses at the air-lens interface. Single lenses 448, 450 are eachpreferably fabricated from a polymeric material such as an acrylic,polystyrene, polycarbonate, or copolymer styrene-acrylonitrile (SAN). Ina preferred embodiment, single lenses 448, 450 are each fabricated fromacrylic.

FIG. 15 illustrates ray path and image orientation through lens module442. The geometrical characteristics of module 442 are defined by anentrance image plane 445a, a front surface 445b, a first bonded surface445c, a second bonded surface 445d, a first inner surface 445e, a secondinner surface 445f, a third bonded surface 445g, a fourth bonded surface445h, a rear surface 445i and an exit image plane 445j. The geometricaland optical parameters of the module are recorded in Table 2. In Table2, surfaces A, B-I and J correspond to image plane 445a, surfaces445b-445i and exit image plane 445j, respectively. Table 2 is asfollows.

                  TABLE 2    ______________________________________                      THICK-                 ABBE    SURFACE RADIUS    NESS     MEDIUM INDEX  NO.    ______________________________________    A       Entrance  2.5      AIR    1.000            Image            Plane    B       7.350     1.4      Acrylic                                      1.492  57.4    C       Plano     24.0     SF2    1.648  33.9    D       Plano     1.5      Acrylic                                      1.492  57.4    E       -9.700    0.2      AIR    1.000    F       9.700     1.5      Acrylic                                      1.492  57.4    G       Plano     24.0     SF2    1.648  33.9    H       Plano     1.4      Acrylic                                      1.492  57.4    I       -7.350    2.5      AIR    1.000    J       Exit Image            Plane    ______________________________________     *dimensions are in millimeters

As indicated in Table 2, the distance between entrance image plane 425aand the first lens surface 445b of lens 448 is approximately 2.5 mm.Similarly, the distance between proximal lens surface 445i of lens 448and exit image plane 445j is also 2.5 mm.

In a preferred embodiment, the relay lens assembly comprises three lensmodules aligned in end to end fashion along a common axis.

It is also envisioned that other relay lens assemblies may beincorporated in the optical system of arthroscope 100. Examples of relaylens assemblies which may be adapted for use with arthroscope 100 aredisclosed in U.S. Pat. No. 4,964,710 to Leiner and U.S. Pat. No.5,188,092 to White and commonly assigned copending U.S. patentapplication Ser. No.: 08/132,007 filed Oct. 5, 1993, application Ser.No. 08/132,009 filed Oct. 5, 1993, and application Ser. No. 08/120,887filed Sep. 13, 1993, the contents of each patent and pending applicationbeing incorporated herein by reference.

Referring now to FIG. 16, the eye lens assembly of optical system isillustrated in detail. Eye lens assembly 460 includes a doublet lens 462having two polymeric lens elements 464, 466 which are bonded to eachother along adjacent end surfaces. Preferably lens element 464 is adouble convex lens and is fabricated from an acrylic while lens element466 is a meniscus lens and is fabricated from a styrene. The geometricalcharacteristics of eye lens assembly 460 are defined by entrance imageplane 465a, surfaces 465b-d and exit image plane 465. Table 3 belowidentifies the optical parameters of the eye lens assemblies.

                  TABLE 3    ______________________________________                      THICK-                 ABBE    SURFACE  RADIUS   NESS     MEDIUM INDEX  NO.    ______________________________________    A        Image    9.1      AIR    1.000             Plane    B        13.500   1.8      Acrylic                                      1.492  57.5    C        -2.000   1.7      Styrene                                      1.590  30.9    D        -5.270   11.0     AIR    1.000    E        Exit Pupil    ______________________________________     *dimensions are in millimeters

As indicated in Table 3, the distance between the image plane 465a andthe first lens surface 465b of eyelens 462 is approximately 9.1 mm.

It is also contemplated that the view finder or eyepiece assembly 220having eye lens assembly 460 therein may be connected to a video cameraadapter to enable the image to be displaced on a monitor for viewing bythe surgical team. It is also possible that the eyepiece assembly 220may be eliminated so that the optical system is connected directly tothe video camera optics.

The optical system of the arthroscope of the present invention providesa clear bright image to the viewer and effectively compensates forpredetermined aberrations in the system such as axial chromaticaberration, lateral chromatic aberration and astigmatism. The opticalsystem can be manufactured sufficiently inexpensively to supply theentire arthroscope as a disposable unit. The principle opticalcomponents including the prism may be molded of plastic thus furtherminimizing the cost of the arthroscope. The glass plano cylinder of therelay lens system can also be manufactured cost effectively.

To the extent not already indicated, it also will be understood by thoseof ordinary skill in the art that any one of various specificembodiments herein described and illustrated may be further modified toincorporate features shown in other of the specific embodiments.

The invention in its broader aspects therefor is not limited to thespecific embodiments herein shown and described but departures may bemade therefrom within the scope of the accompanying claims withoutdepartment from the principles of the invention and without sacrificingits chief advantages.

What is claimed is:
 1. A method for forming an arthroscope having aninclined angle of view comprising the steps of:providing an inner lenstube having optical means disposed therein for transferring an image ofan object and defining an optical axis, said optical means providing avisual field direction angularly offset relative to said optical axis;positioning an annular shim member about an outer peripheral portion ofa distal end portion of said inner lens tube member, an upper portion ofsaid shim member defining an outer positioning surface angularly offsetrelative to an optical axis defined by said optical means; positioningsaid inner lens tube member and said secured shim member within an outertube member; positioning a plurality of optical fibers in a spacedefined between said inner lens tube member and said outer tube member;orientating end portions of said optical fibers about said outerpositioning surface of said shim member to angularly offset said endportions of said optical fibers relative to said optical axis to emitlight in the visual field direction; and mounting a frame portion to aproximal end portion of said outer tube member.
 2. The method accordingto claim 1, wherein said step of positioning said shim member comprisesmolding said shim member about said outer peripheral portion of saidinner lens tube member.
 3. The method according to claim 1 wherein thestep of positioning an annular shim member includes providing saidannular shim member with first and second side edges respectivelydefining first and second guiding surfaces angularly oriented relativeto said optical axis.
 4. The method according to claim 3 wherein thestep of orienting end portions includes arranging end portions of firstand second groups of said optical fibers respectively about said firstand second guiding surfaces of said shim member such that said endportions are angularly oriented relative to said optical axis to emitilluminating light in the visual field direction, and arranging endportions of a third group of optical fibers about said outer positioningsurface of said shim member to emit light in the visual field direction.5. The method according to claim 4 further including the step of forminga curved lip portion adjacent to said distal end portion of said innerlens tube member, said curved lip portion defining an outer peripheralsurface of said inner lens tube member angularly oriented relative tosaid optical axis.
 6. The method according to claim 5 wherein the stepof orientating end portions includes further guiding said third group ofoptical fibers about said outer peripheral surface of said curved lipportion.
 7. The method according to claim 1 wherein the step of mountinga frame portion includes mounting a frame portion having a light guideconnector associated therewith.
 8. The method according to claim 1wherein the step of positioning a shim member includes molding said shimmember directly to said outer peripheral portion of said inner lenstube.
 9. The method according to claim 8 wherein the step of positioninga shim member includes molding said shim member onto said inner lenstube member using replica molding techniques.
 10. A method for formingan arthroscope having an inclined angle of view, comprising the stepsof:providing an inner lens tube having optical means disposed thereinfor transferring an image of an object and defining an optical axis,said optical means providing a visual field direction angularly offsetrelative to said optical axis; positioning an annular shim member aboutan outer peripheral portion of a distal end portion of said inner lenstube member, said shim member including first and second side edgesrespectively defining first and second guiding surfaces angularlyoriented relative to said optical axis, an upper portion of said annularshim member defining an outer positioning surface angularly orientedrelative to said optical axis; positioning said inner lens tube memberand said secured shim member within an outer tube member; positioning aplurality of optical fibers in a space defined between said inner lenstube member and said outer tube member; orientating end portions offirst and second groups of said optical fibers about said first andsecond guiding surface of said shim member to angularly offset said endportions of said optical fibers relative to said optical axis to emitlight in the visual field direction; and mounting a frame portion to aproximal end portion of said outer tube member.
 11. The method accordingto claim 10 further including the step of orientating end portions of athird group of optical fibers about said outer positioning surface ofsaid annular shim member such that said end portions of said third groupare angularly orientated relative to said optical axis to emitilluminating light in the visual field direction.
 12. A method forforming an arthroscope having an inclined angle of view comprising thesteps of:providing an inner lens tube having optical means disposedtherein for transferring an image of an object and defining an opticalaxis, said optical means providing a visual field direction angularlyoffset relative to said optical axis; positioning an annular shim memberto an outer peripheral portion of a distal end portion of said innerlens tube member, said shim member including at least one guidingsurface defining an outer positioning surface, said at least one guidingsurface angularly offset relative to an optical axis defined by saidoptical means; positioning said inner lens tube member and said shimmember within an outer tube member; positioning a plurality of opticalfibers in a space defined between said inner lens tube member and saidouter tube member; orientating end portions of said optical fibers aboutsaid at least one guiding surface of said shim member to angularlyoffset said end portions of said optical fibers relative to said opticalaxis to emit light in the visual field direction; mounting a frameportion to a proximal end portion of said outer tube member, said frameportion having a light guide connector associated therewith; andproviding an illuminator coupler within said light guide connector, saidilluminating coupler including a light transmissive element fortransmitting light received from a light guide to said optical fibers,said light transmissive element being supported in suspended spacedrelation within said illuminating coupler.
 13. The method according toclaim 12 wherein the step of providing an illuminating coupler includesproviding a generally frusto-conically shaped light transmissiveelement.
 14. The method according to claim 13 including the step ofsupporting said light transmissive element within a support member, saidlight transmissive element in spaced relation to inner wall portions ofsaid support member.
 15. The method according to claim 14 wherein thestep of the supporting said light transmissive element includes the stepof supporting said light transmissive element within said support memberwhereby said support member has a generally tapered inner wall portiondefining a generally frusto-conically shaped inner chamber toaccommodate said light transmissive element.
 16. A method for forming anarthroscope having an inclined angle of view comprising the stepsof:providing an inner lens tube having optical means disposed thereinfor transferring an image of an object and defining an optical axis,said optical means providing a visual field direction angularly offsetrelative to said optical axis; providing an outer tube member;positioning an arcuate shim member about an outer peripheral portion ofa distal end portion of said inner lens tube member, said shim memberincluding at least one guiding surface, said at least one guidingsurface angularly offset relative to an optical axis defined by saidoptical means, said arcuate shim member defining a cross-sectionaldimension approximating a maximum inner dimension of said outer tubemember whereby upon positioning said inner lens tube member within saidouter tube member said shim member engages said outer tube member tostabilize said inner lens tube member therewithin thereby facilitatingassembly of said inner lens tube member within said outer lens tubemember; positioning said inner lens tube member and said secured shimmember within an outer tube member; positioning a plurality of opticalfibers in a space defined between said inner lens tube member and saidouter tube member; orientating end portions of said optical fibers aboutsaid at least one guiding surface of said shim member to angularlyoffset said end portions of said optical fibers relative to said opticalaxis to emit light in the visual field direction; and mounting a frameportion to a proximal end portion of said outer tube member.
 17. Themethod according to claim 16 wherein said arcuate shim member includesfirst and second side edges respectively defining first and secondguiding surfaces angularly oriented relative to said optical axis andwherein the step of orienting end portions includes arranging endportions of first and second groups of said optical fibers respectivelyabout said first and second guiding surfaces of said shim member suchthat said end portions are angularly oriented relative to said opticalaxis to emit illuminating light in the visual field direction.
 18. Themethod according to claim 17 wherein said arcuate shim member isannular-shaped defining said first and second side edges and furtherhaving an upper portion defining an outer positioning surfaces angularlyoriented relative to said optical axis, and wherein the step oforientating end portions includes arranging end portions of a thirdgroup of optical fibers about said outer positioning surface of saidannular shim member such that said end portions of said third group areangularly orientated relative to said optical axis to emit illuminatinglight in the visual field direction.